KVM: selftests: Move vcpu_args_set into perf_test_util

perf_test_util is used to set up KVM selftests where vCPUs touch a
region of memory. The guest code is implemented in perf_test_util.c (not
the calling selftests). The guest code requires a 1 parameter, the
vcpuid, which has to be set by calling vcpu_args_set(vm, vcpu_id, 1,
vcpu_id).

Today all of the selftests that use perf_test_util are making this call.
Instead, perf_test_util should just do it. This will save some code but
more importantly prevents mistakes since totally non-obvious that this
needs to be called and failing to do so results in vCPUs not accessing
the right regions of memory.

Signed-off-by: David Matlack <dmatlack@google.com>
Message-Id: <20210805172821.2622793-1-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

tools/testing/selftests/kvm/access_tracking_perf_test.c

@@ -222,8 +222,6 @@ static void *vcpu_thread_main(void *arg)
 	int vcpu_id = vcpu_args->vcpu_id;
 	int current_iteration = -1;
 
-	vcpu_args_set(vm, vcpu_id, 1, vcpu_id);
-
 	while (spin_wait_for_next_iteration(&current_iteration)) {
 		switch (READ_ONCE(iteration_work)) {
 		case ITERATION_ACCESS_MEMORY:

tools/testing/selftests/kvm/demand_paging_test.c

@@ -52,7 +52,6 @@ static void *vcpu_worker(void *data)
 	struct timespec start;
 	struct timespec ts_diff;
 
-	vcpu_args_set(vm, vcpu_id, 1, vcpu_id);
 	run = vcpu_state(vm, vcpu_id);
 
 	clock_gettime(CLOCK_MONOTONIC, &start);

tools/testing/selftests/kvm/dirty_log_perf_test.c

@@ -44,7 +44,6 @@ static void *vcpu_worker(void *data)
 	struct perf_test_vcpu_args *vcpu_args = (struct perf_test_vcpu_args *)data;
 	int vcpu_id = vcpu_args->vcpu_id;
 
-	vcpu_args_set(vm, vcpu_id, 1, vcpu_id);
 	run = vcpu_state(vm, vcpu_id);
 
 	while (!READ_ONCE(host_quit)) {

tools/testing/selftests/kvm/lib/perf_test_util.c

@@ -150,6 +150,8 @@ void perf_test_setup_vcpus(struct kvm_vm *vm, int vcpus,
 			vcpu_gpa = guest_test_phys_mem;
 		}
 
+		vcpu_args_set(vm, vcpu_id, 1, vcpu_id);
+
 		pr_debug("Added VCPU %d with test mem gpa [%lx, %lx)\n",
 			 vcpu_id, vcpu_gpa, vcpu_gpa +
 			 (vcpu_args->pages * perf_test_args.guest_page_size));

tools/testing/selftests/kvm/memslot_modification_stress_test.c

@@ -45,7 +45,6 @@ static void *vcpu_worker(void *data)
 	struct kvm_vm *vm = perf_test_args.vm;
 	struct kvm_run *run;
 
-	vcpu_args_set(vm, vcpu_id, 1, vcpu_id);
 	run = vcpu_state(vm, vcpu_id);
 
 	/* Let the guest access its memory until a stop signal is received */